1. Technical Field
The present invention generally relates to the field of clinical chemistry. More particularly, the present invention relates to a readhead for a diagnostic imaging system that analyzes the color change associated with one or more test areas on sample media following contact thereof with a liquid specimen, such as urine or blood.
2. Background Information
Throughout this application, various patents are referred to by an identifying citation. The disclosures of the patents referenced in this application are hereby incorporated by reference into the present disclosure.
Sample media such as reagent test strips are widely used in the field of clinical chemistry. A test strip usually has one or more test areas spaced along the length thereof, with each test area being capable of undergoing a color change in response to contact with a liquid specimen. The liquid specimen usually contains one or more constituents or properties of interest. The presence and concentrations of these constituents or properties are determinable by an analysis of the color changes undergone by the test strip. Usually, this analysis involves a color comparison between the test area or test pad and a color standard or scale. In this way, reagent test strips assist physicians in diagnosing the existence of diseases and other health problems.
Color comparisons made with the naked eye can lead to imprecise measurement. Today, strip reading instruments exist that employ reflectance photometry for reading test strip color changes. These instruments accurately determine the color change of a test strip within a particular wavelength range or bandwidth. Some instruments may also measure color inconsistencies outside this bandwidth. For example, instruments such as those sold under the CLINITEK® trademark by Bayer Healthcare Diagnostics Division of Bayer HealthCare LLC (Medfield, Mass.) and/or as disclosed in U.S. Pat. Nos. 5,408,535 and 5,877,863 (the '863 patent), both of which are fully incorporated by reference herein, may detect features such as traces of blood within a urine specimen on a MULTISTIX® (Bayer) reagent strip. After the urine specimen contacts the test pad of a MULTISTIX® reagent strip, intact blood cells appear as small green blotches on the yellow test area. These existing strip readers can detect both the overall color of the test pad and the small blotches of green.
As disclosed in the '863 patent, these instruments typically include a Readhead configured to illuminate the test strip and enable images of the illumined test strip to be captured by one or more imagers or detectors such as CCD devices and the like. These imagers tend to be elongated, having a relatively high aspect ratio (ratio of length to width). The high aspect ratio advantageously provides these imagers with a field of view that is sufficiently elongated to capture images of nominally along the entire length of the elongated test strips.
A trade-off, however, associated with these high aspect ratio imagers is that the field of view tends to be relatively narrow, to thus capture a similarly narrow image. The captured image typically represents only a small slice or fraction of the total test area of the test strip. Although this ‘slice’ is generally sufficient to generate useful test results, increased image width may be desirable in many applications, such as to increase the dynamic range of the instrument for improved resolution. Although larger CCD devices may be used to capture wider images, a CCD large enough to capture an image of nominally the entire length and width of the test strip may be prohibitively expensive.
A need therefore exists for an improved diagnostic testing device that efficiently expands the width of an image captured with a high aspect ratio imager.